This invention relates to liquid fuel burner appliances such as campstoves and utility stoves. More particularly, the invention relates to an automatic instant lighting system for liquid fuel burning campstoves.
Liquid fuel campstoves and lanterns for camping and outdoor use are well known and are described, for example, in U.S. Pat. No. 3,876,364, which is owned by The Coleman Company, Inc. Liquid fuel which is used in such campstoves and lanterns can be Coleman fuel, white gas, unleaded gasoline, etc.
In conventional liquid fueled campstoves such as the ones which Coleman has offered for many years, fuel is contained in a pressure vessel or fuel tank into which air is pumped under pressure. As described in U.S. Pat. No. 3,876,364, the fuel tank is equipped with a dip tube which extends to nearly the bottom of the tank. The dip tube is closed at the bottom with the exception of a small diameter orifice through which fuel is allowed to enter. The dip tube has an internal conduit which is open at the bottom and which communicates with the upper part of the pressure vessel above the maximum intended fuel level. The dip tube orifice can be partly blocked by insertion of a needle which is suitably connected to the fuel control system so as to cause it to partly block the orifice during the lighting cycle and to leave the orifice unblocked during the normal burn cycle. This partial blockage during the lighting cycle causes air to be drawn down the space between the internal and outer conduits of the dip tube from an opening at the upper part of the pressure vessel. As this air accompanies fuel up the internal conduit, a mixture of fuel and air more suitable for burning is created to enhance lighting. The air fuel mixture then passes to a generator which is connected to the dip tube by the fuel control system. The generator is a metal tube which passes above the burner of the stove into a venturi assembly which is connected to the burner. Fuel is discharged at high velocity from an orifice or jet at the end of the generator into the venturi where air is aspirated and mixed and fed to the burner as a combustible mixture for burning.
In U.S. Pat. No. 3,876,384, the restricting needle is operated by rotating the fuel control knob. In other appliances, a lever is used to adjust the appliance for starting and running. The lever is moved up to start and then down to run.
In the case of liquid fueled appliances which have a relatively low ratio of fuel delivery required at full output and at minimum output, it is possible to rely upon increases in resistance to the flow of fuel which occur due to heating of the generator to allow air to flow down through the passageway between the inner and outer conduits of the dip tube so as to provide an air rich mixture for lighting and so as to prevent air from filling that passageway and mixing with the fuel when the generator is hot. This system is used on Coleman liquid fueled lanterns which have been sold for many years. Campstoves and utility stoves require a relatively high ratio of heat output between low simmer and full output and it has heretofore not proven possible to achieve the necessary air flow differentials for proper operation of these devices without use of the manually operated system described above.
The foregoing structure for allowing liquid fuel appliances to be lighted when the generator is cold is referred to as an instant lighting system. Liquid fuel appliances which do not include an instant lighting system require some other means for heating the generator during start-up, for example, liquid priming fuel or heating paste.